Linear friction welding (LFW) is a process of joining two components which may be made from the same or different materials. The LFW process typically involves pressing the two components together under a large amount of force and rapidly vibrating the components with respect to one another to generate friction at the interface between the two components. The pressure and movement generate sufficient heat to cause the material at the interface to plasticize. Once the material at the interface begins to plasticize, the vibration is stopped and an increased force is applied. As the plasticized material of both components cools in this static condition, the components are bonded together and a weld is formed. While LFW is suitable in many applications, heretofore, LFW has not been practical for repair welds.
The linear friction welding (LFW) apparatus of this invention, in various embodiments includes a vibrating assembly or assemblies, which simultaneously vibrates both work pieces along the weld axis during the weld process. In one embodiment of this invention, separate vibrating assemblies are used to vibrate each work piece along the weld axis relative to each other. Each vibrating assembly has its own oscillator mechanism with motors and cams that can be moved into and out of phase with that of the other vibrating mechanism to generate the relative movement between the work pieces. In another embodiment of this invention, the apparatus includes a vibrating assembly that uses a single oscillator and two sets of rocker arms supporting carriages operatively connected by a linkage mechanism to simultaneously vibrate both work pieces along the weld axis. In each embodiment of the LFW apparatus of this invention, each vibrating assembly controls the amplitude and frequency of the oscillation during the weld process, but also almost instantly stop the oscillation with no load on the tooling or work piece. Furthermore, vibrating both work pieces relative to one another provides certain mechanical advantages over simply vibrating a single work piece against a fixed or stationary work piece.
In one embodiment, a method of operating a linear friction welding apparatus includes holding a first work piece with a first fixture, holding a second work piece with a second fixture, pressing the first work piece toward the second work piece along a press axis with a press assembly, establishing a selective load between the first work piece and the second work piece with the press assembly while the first fixture and the second fixture are in a fixed position relative to one another, and simultaneously vibrating, with a vibrating assembly spaced apart from the press axis, the first fixture and the second fixture along a single weld axis so that both the first work piece and the second work piece are moved with respect to one another along the single weld axis after establishing the selective load.
The apparatus and method of the present invention may take form in various systems and components, as well as the arrangement of those systems and components. The above described features and advantages, as well as others, will become more readily apparent to those of ordinary skill in the art by reference to the following detailed description and accompanying drawings. The drawings are only for purposes of illustrating exemplary embodiments and are not to be construed as limiting the invention.